Recently, as is seen in British Laid-open Patent No. 2120579, a method has become known in which portions of stones, rocks, or concrete to be crushed are surrounded by a liquid environment, and a high-voltage discharge is generated to create shock waves, thereby crushing the stones, rocks, or concrete.
FIG. 10 shows a so-called Marx generator, which is a power unit for creating discharge shock waves by generating a high-voltage discharge in the aforesaid method. The Marx generator generates a pulse at a discharge electrode 2 with the pulse having a high voltage (50 kV to 800 kV) and a pulse width of about 200 nsec, from an inexpensive power source 1 of smaller voltage (40 kV). For example, as shown in the drawing, six capacitors C1 to C6 are sequentially connected in parallel to the power source 1 via resistors 3a to 3k. In addition, the upstream and downstream sides of each pair of adjacent opposed capacitors C1 and C2, C2 and C3, C3 and C4, C4 and C5, and C5 and C6, are respectively connected by switches S11 to S15, and the last capacitor C6 is connected to the discharge electrode 2.
Specifically, in the Marx generator in FIG. 10, the capacitors C1 to C6 are respectively charged with the current from the power source 1 (40 kV) by opening the switches S11 to S15. Thereafter, the capacitors C1 to C6 are switched from the parallel connection to a serial connection by simultaneously closing the switches S11 to S15, thereby establishing a high-voltage power source of 240 kV as a whole, and a discharge pulse is generated at the discharge electrode 2 with a pulse width of about 200 nsec, for example.
However, in the aforesaid Marx generator, the discharging current flows through the switches S11 to S15, thereby wearing the switches S11 to S15; therefore, disadvantages occur in the performance, reliability, durability, and cost. In addition, there is a disadvantage in that the inductance components of the switches S11 to S15 prevent the generation of "a shorter pulse" which is advantageous in generating shock waves.